1. Field of the Invention
The present invention relates to the extraction of fluids from subterranean formations. In another aspect, the present invention relates to the extraction of fluids from subterranean formations drilled by mud rotary drilled wells. In even another aspect, the present invention relates to the extraction of fluids from mud drilled hydrocarbon wells, water supply wells, and monitoring wells. In still another aspect, the present invention relates to the extraction of a target fluid and mud filtrate down hole and with each of the target fluid and the mud filtrate being produced to the surface via separate tubing. In yet another aspect, the present invention relates to the production of hydrocarbons and mud filtrate down hole and with each of the hydrocarbons and the mud filtrate being produced to the surface via separate tubing. In even still another aspect, the present invention relates to the production of water and mud filtrate down hole and with each of the water and the mud filtrate being produced to the surface via separate tubing. In even yet another aspect, the present invention relates to the extraction of a test sample and mud filtrate down hole and with each of the test sample and the mud filtrate being extracted via separate tubing. It is possible that only one of the hydrocarbon or the mud filtrate may require a production tubing, with the cased wellbore itself being one of the tubings. It is also possible that the mud filtrate may be re-injected downhole into a separate zone of lower pressure that has been depleted or does not contain hydrocarbons or to raise the pressure of another hydrocarbon or water producing zone for enhanced or improved oil recovery.
2. Description of the Related Art
Rotary drilling utilizing a circulating drilling mud is commonly used for drilling wells into the subterranean, non-limiting examples of which include hydrocarbon wells, water wells, and monitoring wells. Basically, rotating hollow drill pipes carry down bentonite and barite infused drilling muds to lubricate, cool, and clean the drilling bit, control downhole pressures, stabilize the wall of the borehole and remove drill cuttings. The drilling mud travels back to the surface around the outside of the drill pipe, called the annulus.
During such drilling mud rotary drilling, in which the well-bore pressure is maintained at a pressure higher than formation pressure, mud filtrate invades porous, permeable formations and the solids in the mud form a mudcake on the borehole wall. In the production of hydrocarbons, “invasion” is generally thought of as mud filtrate simply displacing formation water and any hydrocarbons to some distance away from the borehole wall. The irregularly shaped invaded zone surrounding the borehole wall becomes saturated with mud filtrate. In the production of hydrocarbons, it is not uncommon for the produced fluids to contain some percentage of mud filtrate. This can become an expensive problem, because not only is there loss in revenue because the produced fluid contains less hydrocarbon, there are incurred expenses by the extra cost of transporting the oil/filtrate and the cost of separating the mud filtrate from the oil. Additional costs may occur because almost all mud filtrate, whether it is oil based or is water based contains significant amounts of water (as water sources are drilled through), and water together with water velocity causes corrosion in pipelines. Indeed, water may significantly fill a pipeline over time, reducing the amount of hydrocarbons which may be transported.
There is certainly a need in the art for improved production methods, apparatus and products that provide for production of the desired fluid with ideally no mud filtrate, perhaps just little mud filtrate, or at the very least reduced mud filtrate.
Invasion also affects all shallow-reading tools such as density, neutron porosity and micrologs. These logs had to be interpreted carefully, particularly when water-base filtrate was suspected of displacing oil or gas. Deep-reading resistivity logs designed to see beyond the invaded zone, a few feet from the borehole, often did not see deep enough, and these needed correction to obtain true formation resistivity.
In oil and gas exploration, drill stem testing is a procedure to isolate, stimulate and flow a downhole formation to determine the fluids present and the rate at which they can be produced. Generally, the main objective of drill stem testing is to evaluate the commercial viability of a zones economic potential by identifying productive capacity, pressure, permeability or extent of an oil or gas reservoir. These tests can be performed in both open and cased hole environments and provide exploration teams with valuable information about the nature of the reservoir. Drill stem testing involves deploying a series of tools known as a test bottomhole assembly. A basic drill stem test bottomhole assembly consists of a packer or packers, which act as an expanding plug to be used to isolate sections of the well for the testing process, valves that may be opened or closed from the surface during the test, and recorders used to document pressure during the test. In addition to packers a downhole valve is used to open and close the formation to measure reservoir characteristics such as pressure and temperature which are charted on downhole recorders within the bottomhole assembly.
The following are merely a few of the many patent publications and patents directed to formation testing.
U.S. Pat. No. 2,775,304 to Zandmer issued Dec. 25, 1956, discloses an apparatus for providing ducts between borehole wall and casing. Essentially, plungers moveably supported in bushings fixed in holes through the casing are moved outwardly to engage the wall of the well bore and provide cores surrounded by the sealing material and the bushings, thus affording communication between the wall of the bore hole and the interior of the casing.
U.S. Pat. No. 3,611,799 to Davis issued Oct. 12, 1971, discloses a multiple chamber earth formation fluid sampler for obtaining fluid samples from earth formations wherein a borehole exploring unit supported for movement through the borehole is provide with spaced means for isolating borehole wall formation portions from borehole fluids.
U.S. Pat. No. 4,716,973 to Cobern issued Jan. 5, 1988, discloses a method for evaluation of formation invasion and formation permeability by conducting a series of formation resistivity loggings in the operation of a measurement while drilling (MWD) logging system.
U.S. Pat. No. 5,829,520 to Johnson issued Nov. 3, 1998, discloses a method and apparatus for testing, completion and/or maintaining wellbores using a sensor device. The device is a data acquisition device capable of monitoring, recording wellbore and/or reservoir characteristics while capable of fluid flow control, and the method is for monitoring and/or recording at least one downhole characteristic during testing, completion and/or maintenance of a wellbore. The device includes an assembly within a casing string comprising a sensor probe having an optional flow port allowing fluid flow while sensing wellbore and/or reservoir characteristics. The device also includes a microprocessor, a transmitting device, and a controlling device located in the casing string for processing and transmitting real time data. A memory device is also provided for recording data relating to the monitored wellbore or reservoir characteristics. Examples of downhole characteristics which may be monitored include: temperature, pressure, fluid flow rate and type, formation resistivity, cross-well and acoustic seismometry, perforation depth, fluid characteristic or logging data. With the microprocessor, hydrocarbon production performance maybe enhanced by activating local operations in additional associated downhole equipment, e.g., water shut-off operations at a particular zone, maintaining desired performance of a well by controlling flow in multiple wellbores, zone mapping on a cumulative basis, flow control operations, spacing casing and its associated flow ports in multiple zone wellbores, maintaining wellbore and/or reservoir pressure, sensing perforation characteristics, sensing reservoir characteristics or any number of other operations.
U.S. Pat. No. 5,934,374 to Hrametz et al. issued Aug. 10, 1999 discloses a formation tester (the only embodiment mentioned is electric wireline, and significant downhole power is required) with improved sample collection system for collecting a formation fluid in a chamber at a predetermined pressure and for maintaining the pressure of the collected fluid at a desired level during the retrieval of the chamber to the surface. The formation fluid is pumped into the chamber while a piston exposed to the hydrostatic pressure maintains the chamber pressure at the hydrostatic pressure. During retrieval of the chamber, the pressure in the chamber is maintained at a predetermined level by pumping wellbore fluid to the piston. A control unit at the surface is utilized for controlling the operation of the formation tool.
U.S. Pat. No. 6,301,959 to Hrametz et al. issued Oct. 16, 2001, discloses a focused formation fluid sampling probe that uses two hydraulic lines to recover formation fluids from two zones in a borehole. One of the zones is a guard zone and the other is a probe zone. The guard zone and the probe zone are isolated from each other by mechanical means, with the guard zone surrounding the probe zone and shielding it from the direct access to the borehole fluids. Operation of the tool involves withdrawal of fluid from both zones. Borehole fluids are preferentially drawn into the guard zone so that the probe zone recovers the formation fluid substantially free of borehole fluids. Separation of the guard zone from the probe zone may be accomplished by means of an elastomeric guard ring, by inflatable packers or by tubing. The device can be adapted for use either on a wireline or in an early evaluation system on a drillstring.
U.S. Pat. No. 6,786,086 to Hashem issued Sep. 7, 2004, discloses a method for determining the in-situ effective mobility of hydrocarbons in a formation layer and the effective permeabilty of a formation, in which a formation test tool, having a fluid analyzer, induces sample fluid to flow from the formation, the sample being analyzed and discarded where it includes fluid from the invaded zone, so as to perform the pressure test on uncontaminated formation fluid.
OTC 18201, Advances in Fluid Sampling With Formation Testers for Offshore Exploration, C. Del Campo et al., Offshore Technology Conference, May 1-4, 2006, discloses that formation fluid samples provide valuable information for field development, and that drilling mud filtrate contamination reduces the sample quality drastically, and the current industry technique to obtain clean fluid samples requires a long pumping time. This can be costly, especially in deep offshore wells. Also disclosed is a new formation fluid sampling apparatus which separates filtrate contamination efficiently from the virgin reservoir fluid; the fluid sample cleans up much faster than with the conventional approach. In addition to the new sampling apparatus, downhole fluid characterization techniques, including contamination monitoring, composition measurement, and single-phase assurance, are presented. The apparatus provides real-time fluid property information, and helps ensure that representative samples are obtained.
Wireline Sampling Technology Enables Fluid Sampling Without Contamination JPT, September 2006, discloses a focused sampling technique using a new wireline sampling tool that was applied successfully in the Cairn Energy-operated Bhagyam field, Rajasthan, northwest India. Favorable results were achieved in this field, formation characteristics of which-highly viscous, waxy crude and oil-based mud (OBM)-had presented numerous challenges in obtaining good representative reservoir-mud samples, even after long pumping times. Of the 18 samples collected from two wells, 83% were of pressure/volume/temperature (PVT) quality, and 33% of the samples showed zero mud-filtrate contamination. The sampling technique separates drilling-mud-filtrate contamination efficiently from the formation fluid in the early stage of the sampling process, allowing cleaner samples and faster collection compared to traditional probe-type wireline formation testers.
Wireline and While-Drilling Formation-Tester Sampling with Oval, Focused, and Conventional Probe Types in the Presence of Water- and Oil-Base Mud-Filtrate Invasion in Deviated Wells, Abdolhamid Hadibeik et al., Society of Petrophysicists and Well Log Analysts 50th Annual Logging Symposium, Jun. 21-24, 2009, quantifies the viability of sampling in the drilling environment by way of numerical simulations, and considers the dynamic nature of invasion while drilling when using both new and conventional probe configurations to retrieve fluid samples. The prior art assumed a time-constant rate of invasion that was close to that of the final stages of invasion. Furthermore, most simulations of wire line formation-tester measurements assumed that invasion ended at the time when fluid pumpout began. Both of these assumptions are optimistic for a drilling tool. To more realistically simulate the invasion during drilling, a mudcake model is used that continues to grow in thickness and sealing effectiveness during invasion and throughout the sampling process. With this mudcake model there are higher rates of invasion soon after drilling. Simulation results focus on scenarios in which water-base mud (WBM) and oil-base mud (OBM) invade an oil-bearing zone. This paper also studies the accuracy of functions used to estimate contamination in an OBM environment. The base model consists of a typical probe-type tool in a vertical well wherein fluid samples are retrieved using a time-constant flow rate. Invasion time is varied from 1 to 48 hours to compare drilling and wireline sampling tools. This paper quantifies mudcake sealing effectiveness, as well as the effect of borehole deviation. Oval (elongated) and focusing guard-style probes are compared to standard probe configurations in various petrophysical rock types. Simulations of fluid cleanup times for a variety of rock types and wellbore deviation angles indicate that the oval focused probe retrieves the cleanest fluid sample in the least amount of time.
Improved Techniques for Acquiring Pressure and Fluid Data in a Challenging Offshore Carbonate Environment, K. D. Contreiras et al., Search and Discovery Article No. 40433, posted Aug. 10, 2009, discloses that the combination of low permeability, oil base mud and near saturated oils presents one of the most challenging environments for fluid sampling with formation testers. Low permeability indicates that the drawdown while sampling will be high but this is contra-indicated for oils that are close to saturation pressure. Prior art solutions suggest reducing the flow rate but in wells drilled with OBM an unacceptably long clean-up time would result.
The Pinda formation in Block 2 offshore Angola presents just such a challenge. Formation mobilities are in the low double or singledigits, saturation pressure is usually within a few hundred psi of formation pressure and borehole stability indicates that the wells must be drilled with oil base mud. Further disclosed is a two-step solution was used, that first includes a high efficiency pretest-only WFT in order to quickly gather formation pressure data and mobility data. This data is then used to design the sampling string which is a combination of an inflatable dual packer with focused probe. Further disclosed is the decision process that governs the choice of pump, displacement unit, probe and packer. Particular attention is paid to the unique pump configurations that are required to effectively manage the drawdowns when using the probe and also to allow sufficient flow rate when using a dual packer.
Comparison of Wire line Formation-Tester Sampling with Focused and Conventional Probes in the Presence of Oil-Base Mud-Filtrate Invasion, Mayank Malik et al., Petrophysics, Vol. 50, No. 5, October 2009, discloses that in the course of fluid sampling, varying concentrations of oil base mud (OBM) will lead to variations of fluid properties such as viscosity, density, and gas-oil ratio (GOR). A focused probe can be useful in reducing OBM contamination by diverting flow into different channels without compromising fluid pumpout time. However, it is important to properly quantify the relative performance of focused and conventional probes for a wide range of field conditions. Further disclosed is the performance of different probes under the same simulated field conditions and for a comprehensive set of petrophysical and fluid properties. Results indicate that sample quality generally improves when the flow is split between the guard and sample probes, but the specific amount of improvement depends on probe geometry, fluid composition, and formation properties. Permeability anisotropy, presence of a flow boundary, and lack of mud-filtrate invasion can help to improve sample quality. In addition, fluid cleanup can be accelerated by altering both the probe design and the flow-rate ratio between the sample and guard fluid streams, thereby leading to increased pressure differential between the sample and guard areas and enhancing the “coning” of the mud-filtrate invasion front.
History Matching of Multiphase-Flow Formation-Tester Measurements Acquired with Focused-Sampling Probes in Deviated Wells, Renzo Angeles et al., Petrophysics, February 2011, discloses that complex tool and rock-formation properties are becoming prevalent in formation-testing operations. As hydrocarbon exploration shifts toward high-cost and high-risk frontiers, it is now common to measure pressures and to acquire fluid samples in deviated and sidetrack wellbores. At the same time, standard analytical and numerical methods used for the interpretation of formation-tester measurements continue to be based on restricting physical assumptions such as single-phase flow, over-simplistic mud-filtrate invasion radial profiles, and vertical wellbores. Interpretation of transient focused-sampling measurements acquired in wells drilled with oil-based mud (OBM) is particularly challenging. The combination of miscibility (between mud-filtrate and in-situ oil) and non-standard probe geometry requires more petrophysically reliable interpretation methods than currently available with single-phase analytical techniques. Further disclosed is the application of a three-dimensional (3D) multiphase-flow method to interpret two field data sets acquired with focused-sampling probes in deviated wells. The interpretation method includes the dynamic effects of OBM mud-filtrate invasion and their corresponding impact on fluid properties, such as viscosity and density, in the near-wellbore region. Numerical simulations verify the consistency of the measurements and quantify the role played by petrophysical, fluid, and geometrical properties on the time evolution of the measurements. Adjustments are made to key petrophysical properties involved in the simulations to reproduce transient measurements of pressure and GOR acquired with a commercial focused fluid-sampling probe. In addition, resistivity logs are numerically simulated to infer the spatial distribution of fluids in the near-borehole region prior to the onset of fluid sampling. Sensitivity studies further appraise the uncertainty of permeability estimates due to wellbore deviation, OBM filtrate viscosity, and radius of invasion. Further disclosed is that irreducible water saturation was influential to determining the spatial distribution of fluids around the well bore as it affected both the separation of apparent resistivity curves and the early-time portion of pressure transient measurements; simulation results also indicate that the angle of wellbore deviation can bias permeability estimates especially for cases of high-permeability formations as well as for the case of large viscosity contrasts of the fluids involved during invasion; and that numerical simulation and history matching of formation-tester measurements acquired under complex environmental conditions is a reliable procedure to diagnose noise, biases, and inconsistencies in transient measurements otherwise undetectable with standard interpretation methods.
U.S. Pat. No. 8,109,140 to Tustin, et al., issued Feb. 7, 2012, discloses a reservoir sampling apparatus that is described as having at least one probe adapted to provide a fluid flow path between a formation and the inner of the apparatus with the flow path being sealed from direct flow of fluids from the borehole annulus with a heating projector adapted to project heat into the formation surrounding the probe and a controller to maintain the temperature in the formation below a threshold value.
U.S. Pat. No. 8,297,364 to Agrawal, et al., issued Oct. 30, 2012, discloses a telescopic unit with dissolvable barrier wherein the telescopic member includes, at least a central component and a barrier disposed within the central component, the barrier has a selectively tailorable dissolution rate curve and has structural properties enabling the containment of high pressure prior to structural failure of the barrier through dissolution.
SPE 162345, Simulation Modeling for Optimized LWD Fluid Sampling Under Different Invasion Profiles by Samarth Agrawal et al, Society of Petroleum Engineers, Abu Dhabi International Petroleum Exhibition & Conference, Nov. 11-14, 2012, discusses the effects of dynamic invasion processes on Logging While Drilling (LWD) fluid sampling and compares its performance with Wire Line (WL) based fluid sampling. The results of the simulation study performed revealed that when the wait time after the drilling is optimized, LWD can provide cleaner samples in shorter cleanup time than WL sampling. It also revealed that the reservoir fluid breakthrough time would be shorter in LWD sampling compared to that of WL. It also discloses that with proper modeling, an optimized sampling program can be executed to meet the objectives of the LWD sampling operations in the most economic manner.
In spite of the advances in the prior art, there is still a need in the art for methods, apparatus and products for overcoming invasion and extracting a target fluid from the subterranean separate from extracting mud filtrate.
There is another need in the art for methods, apparatus and products for overcoming invasion and extracting a target fluid from the subterranean that is free of, relatively free of, or has a lesser amount of mud filtrate.
There is even another need in the art for methods, apparatus and products for overcoming invasion and producing a target fluid and mud filtrate through separate channels.
There is still another need in the art for methods, apparatus and products for overcoming invasion and producing hydrocarbons and mud filtrate through separate tubing/piping to the surface.
There is yet another need in the art for methods, apparatus and products for formation sampling, testing, and/or analysis that extracts formation fluid in a manner that is free or relatively free of the mud filtrate.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.